, Volume 110, Issue 2, pp 271-277,
Open Access This content is freely available online to anyone, anywhere at any time.

Mid-IR difference frequency laser-based sensors for ambient CH4, CO, and N2O monitoring

Abstract

A new mid-infrared sensor platform is described, which combines difference frequency generation (DFG)-based tunable laser sources with simple direct absorption spectroscopy. DFG lasers operating in the 3–5 micron window are tuned to access a variety of species in the C–H, N–O, and C–O stretch regions. The sensors are capable of sub-ppb detection of key greenhouse gas species as well as common pollutants and tracer species. Specific examples of sensor data obtained for methane, nitrous oxide, and carbon monoxide are presented, including relevant time series data and associated Allan Variances. The platform provides a cost-effective alternative to other laser-based approaches in some cases, performing at similar or superior levels. Emphasis on achieving key performance metrics driven by World Meteorological Organization guidelines for Global Air Watch program and other applications is highlighted.